The invention is directed to an apparatus and method for destroying the metallic portion of an elongate medical instrument, such as a hypodermic needle or scalpel for example.
Conventionally, medical instruments such as hypodermic needles, syringes, scalpels, sutures and other metallic cutting means require careful disposal by inserting the instrument into an authorised container. These containers are designed to ensure that the disposal of the instrument does not cause any accidental cuts or punctures to caregivers or others involved in handling the waste.
The risk of accidental exposure to common bacteria, viruses and contraction of communicable diseases has always been a well known fact in such occupations. However recently, as a result of the extremely grave consequences of H.I.V. infection, the need to prevent accidental exposure has become literally a matter of life and death.
Questionable disposal practices have resulted in infected syringes washing up on populated beaches and as a result not only the medical profession but also the general public are painfully aware of the risks involved in improper or careless disposal.
The proper disposal of used medical instruments is a very serious task which requires attention to detail to ensure that risk of infection during disposal does not occur. However as long as the instrument remains capable of puncturing or cutting the skin, there remains a high risk of exposure to infection. Most prior art disposal focuses on the provision of superior containers which seal in the contents.
A different approach has also been taken wherein the cutting or puncturing capacity of the instrument is eliminated, thereby reducing the risk to that of common contaminated medical waste. The sharp metallic portions being removed or dulled reduces the risk of accidental infection substantially One example of such a device is described in U.S. Pat. No. 5,288,964 wherein high voltage is passed through the entire length of an elongate metal instrument to melt the metal portions. The electrical resistance of passing a current through stainless steel instruments is high which results in heat to melt the metal. However the electrical power demands of such a device are so high as to prevent common acceptance.
Considerable advantages exist however for such an approach. The high heat eliminates many bacterial and viral infection risks, and the destruction of sharp metallic portions minimises the risk of accidental skin puncture or cutting.
It is desirable therefore to produce a device which destroys or disarms the sharp portions of such instruments, preferably with high heat to disinfect if possible, while minimising electrical power consumption. By reducing the electrical demands of a device to generally available primary 110 volt power, the lower cost and portability increase the probability of commercial acceptance.
In accordance with the invention is provided a device and method which overcomes the aforementioned disadvantages in a novel manner. The invention provides an improved method and device for destroying metallic portions of elongate medical instruments, with reduced electrical power demands relative to the prior art.
Briefly, while the prior art requires the entire metal portion to be subjected to electrical current, the invention passes current through a narrow band of the metallic instrument. As the electrical resistance in such a narrow band heats up the band to melting or burning, the instrument is progressively advanced thereby consuming the metallic instrument in a progressive fashion rather than as a whole.
The electrical power consumption of experimental devices has been relatively low enabling hypodermic needles of 14 to 28 gauge to be destroyed using power supplies ranging from 3.15 Volts to 12 Volts. These voltages can be supplied by wet cell storage batteries dry cell battery packs, alkaline batteries, nickel-cadmium batteries or appropriate transformers with 110 volt input. Tests confirm that temperatures in the range of 2800 to 3000 degrees Fahrenheit (1500 to 1650 degrees Celsius) are generated in the exposed metal shaft of the stainless steel portion of such needles. These temperatures, by heat conduction, heat the encapsulated needle portion to temperatures of 1400 to 1600 degrees Fahrenheit (750 to 875 degrees Celsius) disinfecting these areas thereby remaining.
Residual metallic debris resulting from the process is minimal. For example, in one test it was estimated that the debris resulting from disposal of 10 needles is merely 0.3 grams. Of course the remaining non metallic portions of syringes etc. are disposed of in the conventional manner. However any risk of accidental puncture and degree of infectious contamination is substantially reduced as a result.
Specifically, the invention provides a method of destroying a metallic portion of an elongate medical instrument having a longitudinal axis, a tip and shaft, the method comprising the steps of: locating the instrument in a position wherein the tip of the instrument electrically engages a contact surface of a first and second electrode, each electrode having said electrical contact surface disposed in opposition and separated by a gap, and each electrode in electrical contact with power source means for creating an electrical potential difference between the electrodes, the potential difference being sufficient to induce electrical resistance burning of the tip of the instrument when an electrical current is passed through the tip between the electrodes; and progressively advancing the instrument and the electrodes longitudinally relative to each other, whereby the burning of the tip of the instrument progressively consumes the shaft as the burning tip advances from the start position to a finish position continuously in electrical contact with each electrode.
Also in accordance with the invention is provided a device for destroying a metallic portion of an elongate medical instrument having a longitudinal axis, a tip and shaft, the device comprising: a housing; first and second electrodes in the housing, each electrode having an electrical contact surface disposed in opposition and separated by a gap; means for moving the instrument to a start position wherein the tip of the instrument electrically engages the contact surface of each electrode; power source means for creating an electrical potential difference between the electrodes, the potential difference being sufficient to induce electrical resistance burning of the tip of the instrument when an electrical current is passed through the tip between the electrodes; and advancing means for progressively advancing the instrument and the electrodes longitudinally relative to each other, whereby the burning of the tip of the instrument progressively consumes the shaft as the burning tip advances from the start position to a finish position continuously in electrical contact with each electrode.